Not Applicable
Not Applicable
Not Applicable
The present invention relates to float operated valves of the type employed for controlling venting of fuel vapor during filling of a fuel tank on board a motor vehicle and particularly relates to systems of the type wherein the tank vent is connected to discharge to a vapor recovery or storage canister. Typically in present high volume production of motor vehicles, a charcoal-filled canister is connected to a vapor vent in the fuel tank; and, the canister is connected through an electrically operated purge valve to the engine inlet manifold. The electrically operated valve is controlled by an electronic control unit (ECU) which controls flow of fuel vapor from the canister to the engine inlet manifold during engine operation; and, the control valve is closed when the engine is not running.
In the aforesaid type fuel tank vapor vent systems, it is necessary to control the venting of fuel vapor to the canister during filling of the fuel tank when the engine is not running in order to prevent liquid fuel from entering the vent and the charcoal canister. Heretofore, float operated vent valves have been employed to close the fuel tank vapor vent to the canister when the fuel reaches a predetermined level in the tank.
However, problems have been encountered in designing and constructing a float operated valve which will close at the desired liquid fuel level or float position. The float must provide sufficient force to overcome the xe2x80x9cBernoullixe2x80x9d effect as the vent valve reaches the closed position and the velocity of the vapor flowing to the vent increases significantly due to the decreasing area of the passage over the vent valve seat. Thus, the buoyancy of the float in the liquid fuel must be sufficient to provide adequate force to overcome the Bernoulli effect and positively close the vent valve against the vent port seat. However, when the float buoyancy provides sufficient force to positively close the vent valve against the Bernoulli effect on an annular valve seat, corking or sticking of the valve has been experienced; and, upon subsequent dropping of the fuel level in the tank from consumption during engine operation, the float gravitational forces have been found in some instances to be insufficient to reopen the valve.
A known on-board refueling vapor recovery valve which has been utilized to overcome this problem is that shown and described in U.S. Pat. No. 5,605,175 issued to Bergsma, et al. which utilizes a resilient valve member having one end attached to the valve body or housing with the opposite end attached to the float for providing a peel-away action to thereby overcome any xe2x80x9ccorkingxe2x80x9d or sticking of the valve member as the liquid fuel level in the tank drops below the level which causes the valve to close.
However, the aforesaid fuel vapor vent control valve of Bergsma, et al. has the disadvantage that in high-volume mass production such as required for passenger car and light truck vehicles, it has been found difficult to assemble the valve member to the body and the float and install the float in the valve housing and complete the valve assembly. This arrangement has thus proven to be not only difficult and time consuming but has resulted in a costly construction given the competitive nature of the automotive marketplace.
Another prior art float type fuel tank vapor vent valve is shown in FIG. 21, where a flexible valve member has one end anchored to the float and the other end free. This arrangement has proven to be generally unsatisfactory in service.
Thus, it has been desired to provide an improved fuel tank vapor vent control valve which is simple and easy to assemble in mass production yet provides a relatively low manufacturing cost.
The present invention provides a float operated fuel vapor vent control valve for a motor vehicle fuel tank installation which may be of the type either attached to the upper wall of the fuel tank through an aperture in the tank wall; or, may be mounted within the tank as for example through the fuel level sender mechanism aperture and connected to a vent port through the wall of the fuel tank. The float operated valve employs a resilient valve member formed in a relatively thin flat ribbon-like configuration which may be bowed into a hook-shaped configuration formed in a flat configuration with the opposite ends thereof attached to the float in spaced relationship. One of the ends of the resilient valve member is disposed and constrained for limited movement in a direction perpendicular to the direction of movement of the float and the opposite end constrained, but undergoing limited movement relative to the float in a direction parallel to that of float movement. This limited movement of one end of the valve member permits the valve member to maintain a low stiffness or high degree of flexibility even when drawn toward the vent port seat by the Bernoulli effect as the valve nears the closed position.
The resilient valve member in the float valve assembly of the present invention is formed preferably of elastomeric material and may be either cut from flat sheet stock and curved to a hooked configuration at assembly or may be molded to the hook configuration or cut from an extrusion. The valve member is installed on the float by either snap locking with integrally formed attachments or may be frictionally assembled and retained by deformation of the float material, as for example, by heat staking. The flexibility of the relatively thin elastomeric valve member of the present invention coupled with the limited movement of one end in its attachment to the float in a direction perpendicular to the direction of movement of the float and the lateral movement of the opposite end provides a highly flexible member which can readily seal on the vapor vent port and yet just as readily, peel away therefrom upon lowering of the float as fuel is consumed from the tank.
The present invention thus provides a unique and novel way of controlling fuel vapor flow through a vent in a fuel tank and provides a valve construction therefor which is easy to assemble and relatively low cost for high volume mass production.